This invention relates to a cargo ship for transporting not fired iron ore pellets (hereinafter termed cold pellets) from a remotely located not firing pellet plant wherein the cold pellets on board are heated to a suitable temperature by a suitable heating device installed in the holds so as to accelerate the hydration reaction of a binder such as cement and to remove excessive water by evaporation.
Since the cold pellets are prepared by bonding together fine powders of iron ore with a binder such as cement or the like, it is necessary to age the cold pellets for about four weeks in order to give strength to the pellets sufficient to withstand the handling operation for loading and unloading. However, the speed of the hydration reaction of cement is low, and usually several percent of not yet reacted water remains in the pores of the pellets. It has been determined by experiments that the crushing strength of the pellets can be increased by twofold or more when such residual water is removed by heating pellets to a temperature of from 100.degree. to 200.degree.C.
The crushing strength of the cold pellets is generally about one half of that of the fired pellets so that when heated to the temperature described above the mechanical strength of the cold pellets can be increased to a value comparable with that of the fired pellets for use as the raw material to be charged in blast furnaces. Where a large number of cold pellets containing a large quantity of water is charged in a blast furnace, the temperature of the gas exhausted from the furnace top is decreased thus decreasing the efficiency of a dust collector associated with the blast furnace.
For this reason, it is advantageous to dry cold pellets before use with the heat of exhaust gas from an engine or boiler while they are being transported by a ship. The use of the heat of exhaust gas decreases the cost of heating the cold pellets and eliminates any drying step after unloading. Moreover, the mechanical strength of the cold pellets is increased before unloading so that it is possible to decrease crushing of the cold pellets during unloading and subsequent handling.